At 05.20 hours on 5 Aug 1941, U-75 attacked convoy SL-81 west of Ireland and observed a column of fire and water after a first hit and a column of water after a second hit. Ringelmann then had to dive and was not able to make further observations. The two ships hit were the Harlingen and the Cape Rodney.

Three crew members from the Harlingen (Master Jack Willingham) were lost. The master, 34 crew members and four gunners were picked up by HMS Hydrangea (K 39) (T/Lt J.E. Woolfendon, RNR) and landed at Gourock.